07-19-2014
• http://www.space.com, By Elizabeth Howell
United Launch Alliance's (ULA) Atlas 5 rocket is the workhorse of heavy satellite launches in the United States, but the booster requires a Russian RD-180 engine to get off the ground.

Recent geopolitical disputes between Russia and the United States have thrown this arrangement, which has been in place for decades, into turmoil. In Twitter remarks in May, Russian Deputy Prime Minister Dmitry Rogozin threatened to ban all sales of RD-180 engines to the United States intended for use in military launches.

"If you look at what has happened to us now in the past few months, it points to a vulnerability," Gen. William Shelton, head of Air Force Space Command, told senators in remarks broadcast on the web from Washington, D.C.